The invention is based on a fuel injection nozzle of the general type described in the main claim. Fuel injection systems have a comparatively long period of time available for the injection during starting or operation in neutral gear or under light partial load, while this time is comparatively short at higher rpms. The diameter of the nozzle, the stroke of the needle, the closing force and thus the injection pressure are mostly determined by the full-load quantity at maximum rpm. Based upon this, the stroke of the valve needle is relatively uncontrolled during periods of low rpm, especially during starting as well as during operation in neutral gear or under low loads. This makes it possible for the valve needle to open fully because of a pressure surge and the entire, relatively small quantity of fuel is injected at once. This causes relatively noisy running of the engine. On the other hand, it is also possible that the valve needle may begin to move erratically because of oscillations of the spring or pressure waves in the supply line, which results in the so-called cold-start hammering of the engine.
In order to control the movements of the valve needle during starting or low rpm, it is known to provide a so-called pressure step, i.e. the forces acting on the valve needle in the direction of the opening are decreased, e.g. by disengagement of the pressure surfaces; or the forces acting in the direction of closure are increased, e.g. by addition of a spring. Both courses lead to a pressure step in regard to the injection pressure, which is generally desired within the area of between 10 and 30% of the opening lift of the valve needle. These known fuel injection nozzles, however, are comparatively expensive to make, since these nozzles are mostly made in small production runs, which therefore require a comparatively high production outlay. Furthermore, few production parts of large-scale production injection nozzles can be utilized.